Balanced gain and loss in Bose-Einstein condensates without PT symmetry

Balanced gain and loss renders the mean-field description of Bose-Einstein condensates PT symmetric. However, any experimental realization has to deal with unbalancing in the gain and loss contributions breaking the PT symmetry. We will show that such an asymmetry does not necessarily lead to a system without a stable mean-field ground state. Indeed, by exploiting the nonlinear properties of the condensate, a small asymmetry can stabilize the system even further due to a self-regulation of the particle number.Comment: 7 pages, 6 figure

The relative roles of CO2 and palaeogeography in determining Late Miocene climate: results from a terrestrial model-data comparison

The Late Miocene (∼11.6–5.3 Ma) palaeorecord provides evidence for a warmer and wetter climate than that of today and there is uncertainty in the palaeo-CO2 record of at least 150 ppmv. We present results from fully coupled atmosphere-ocean-vegetation simulations for the Late Miocene that examine the relative roles of palaeogeography (topography and ice sheet geometry) and CO2 concentration in the determination of Late Miocene climate through comprehensive terrestrial model-data comparisons. Assuming that the data accurately reflects the Late Miocene climate, and that the Late Miocene palaeogeographic reconstruction used in the model is robust, then results indicate that the proxy-derived precipitation differences between the Late Miocene and modern can be largely accounted for by the palaeogeographic changes alone. However, the proxy-derived temperatures differences between the Late Miocene and modern can only begin to be accounted for if we assume a palaeo-CO2 concentration towards the higher end of the range of estimates

Modality of the Tropical Rain Belt Across Models and Simulated Climates

The tropical rain belt varies between unimodal and bimodal meridional precipitation distributions, both regionally and on seasonal to geological time scales. Here we show that this variation is largely driven by equatorial precipitation inhibition, and quantify it using an equatorial modality index (EMI) that varies continuously between 1 and 2 for purely unimodal and bimodal distributions. We show that tropical modality is a fundamental characteristic of tropical climate, which we define as annual-mean EMI. We examine large-scale aspects of tropical modality across 73 climate models from phases 5 and 6 of the Coupled Model Intercomparison Project, 45 paleo simulations (;300 million years ago to present), and observations. We find increased tropical modality to be strongly related to increased width of the tropical rain belt, wider and weaker meridional overturning circulation, colder equatorial cold tongues, and more severe double intertropical convergence zone bias in modern climate models. Tropical sectors (or global zonal means) with low tropical modality are characterized by monsoonal seasonal variations (i.e., seasonal migrations of rainbands following the sun). In sectors with high tropical modality we identify three important seasonal modes: (i) migration of the precipitation distribution toward the warmer hemisphere, (ii) variation in the latitudinal separation between hemispheric rainbands, and (iii) seesaw variation in the intensity of the hemispheric rainbands. In high tropical modality sectors, due to contrasting shifts of the migration and separation modes, counter to general wisdom, seasonal migrations of tropical rainbands cannot be generally assumed to follow the sun.</p

Climate model and proxy data constraints on ocean warming across the Paleocene-Eocene Thermal Maximum

Constraining the greenhouse gas forcing, climatic warming and estimates of climate sensitivity across ancient large transient warming events is a major challenge to the palaeoclimate research community. Here we provide a new compilation and synthesis of the available marine proxy temperature data across the largest of these hyperthermals, the Paleocene-Eocene Thermal Maximum (PETM). This includes the application of consistent temperature calibrations to all data, including the most recent set of calibrations for archaeal lipid-derived palaeothermometry. This compilation provides the basis for an informed discussion of the likely range of PETM warming, the biases present in the existing record and an initial assessment of the geographical pattern of PETM ocean warming. To aid interpretation of the geographic variability of the proxy-derived estimates of PETM warming, we present a comparison of this data with the patterns of warming produced by high pCO2 simulations of Eocene climates using the Hadley Centre atmosphere-ocean general circulation model (AOGCM) HadCM3L. On the basis of this comparison and taking into account the patterns of intermediate-water warming we estimate that the global mean surface temperature anomaly for the PETM is within the range of 4 to 5°C

Author Correction: Climatic and tectonic drivers shaped the tropical distribution of coral reefs

The original version of this Article contained an error in Figs. 4, 5, in which the x-axes labels read 106 km2 instead of 105 km2. This has been corrected in both the PDF and HTML versions of the Article. The original version of the Supplementary Information associated with this Article contained an error in Supplementary Figures 6, 8, 11, in which the x-axes labels read 106 km2 instead of 105 km2. The HTML has been updated to include a corrected version of the Supplementary Information.</p

Cognitive fusion and post-trauma functioning in veterans: Examining the mediating roles of emotion dysregulation

When cognitively fused, people have difficulty accepting and clearly perceiving their internal experiences. Following trauma, emotional non-acceptance and emotional non-clarity have been associated with post-trauma functioning. The aim of the present study was to integrate theory and research on cognitive fusion and posttrauma functioning to evaluate a theory-based model in which emotion dysregulation—specifically, emotional non-acceptance and emotional non-clarity—mediated the association between cognitive fusion and post-trauma functioning in a veteran sample. Participants were 149 veterans with a history of military-related trauma. Veterans completed measures of cognitive fusion, emotion dysregulation, posttraumatic stress disorder (PTSD) symptoms, and life satisfaction. Overall, emotion dysregulation and PTSD symptoms mediated the fusion-posttrauma functioning association in theoretically consistent ways. More specifically, fusion was related to PTSD through emotional non-clarity and fusion was related to goal dysregulation through emotional non-acceptance and PTSD. Our findings indicate that fusion impacts different aspects of post-trauma functioning through different mediators. How these different pathways could impact clinical decision making are discussed

Precessional drivers of late Miocene Mediterranean sedimentary sequences: African summer monsoon and Atlantic winter storm tracks

Cyclic sedimentary patterns in the marine record of the Mediterranean Sea have been consistently correlated with orbitally‐driven shifts in climate. Freshwater input driven by the African summer monsoon is thought to be the main control of such hydrological changes, where the runoff signal is transferred from the eastern to the western Mediterranean. The geological record from the Atlantic margin also contains precession‐driven dilution cycles that have been correlated with the sedimentary sequences in the western and eastern Mediterranean despite the lack of a direct connection with the basin. In these regions, Atlantic winter storms have also been invoked to explain the wet phases. In the absence of seasonally‐resolved proxy data, climate simulations at high temporal resolution can be used to investigate the drivers of Mediterranean hydrologic changes both on precessional and seasonal timescales. Here, we use the results of 22 ocean‐atmosphere‐vegetation simulations through an entire late Miocene precession cycle. These show that the African summer monsoon drives the hydrologic budget in the Eastern Mediterranean during precession minima, while the western marginal basins are generally dominated by local net evaporative loss. During precession minima, the western Mediterranean and the Atlantic margin are also influenced by enhanced winter precipitation from the Atlantic storm tracks. We can, therefore, identify two different moisture sources affecting the circum‐Mediterranean area, characterized by the same phasing with respect to precession, but with opposite seasonality. This supports the interregional correlation of geological sections in these areas, as we show for the Messinian and speculate for other time periods